Process of elimination of bacteria in shellfish of shucking shellfish and an apparatus therefor

ABSTRACT

The invention relates to a process for eliminating pathogenic organisms from raw food products, such as raw shellfish, whereby the molluscan shellfish is exposed to hydrostatic pressure of relatively high value, for example between 20,000 p.s.i. to 50,000 p.s.i. for 1-15 minutes. The process is conducted at ambient temperatures, leaving the raw shellfish substantially unaffected, in its desired raw state, such that the pathogenic organisms are destroyed, while sensory characteristics of the raw shellfish remain high. The same process can be used for shucking oysters without any mechanical force. A high pressure processor for elimination of bacteria in raw food products is disclosed.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on my provisional applications SerialNos. 60/071,819 filed on Jan. 20, 1998, 60/074,582 filed on Feb. 13,1998, and 60/086,484 filed on May 26, 1998, the full disclosures ofwhich are incorporated herein.

BACKGROUND OF THE INVENTION

[0002] This application relates to a process of treatment of rawmolluscan shellfish, and more particularly to a process for destroyingbacteria in shellfish, such as for example oysters.

[0003] In recent years, considerable attention has been paid in themedia to tragic results of consumption of raw oysters where theindividuals became infected with life threatening pathogenic organisms.Such bacteria as Vibrio Vulnificus live in marine environment,especially in warm waters, usually higher than 25° C.

[0004]Vibrio Vulnificus has been isolated from estuarine and marinewaters of the U.S. Gulf Coast, east coast, and west coast; it was alsoreported on other continents. The bacteria may transfer from water tothe shellfish inhabiting the body of water, especially filter-feedingmollusks, where bacteria can multiply mostly in the gut region.

[0005] Vibrio is a genus of motile curved and rod-shaped Gram-negativebacteria. Other well-known vibriones are Vibrio cholerae and VibrioParahaemolyticus. Vibrio Parahaemolyticus is a common cause ofgastroenteritis in some cultures, where consumption of food isparticularly high, such as for example Japan.

[0006]Vibrio Vulnificus is a halophilic species, the strains of whichare similar to Vibrio Parahaemolyticus and Vibrio alginolyticus. VibrioVulnificus thrives in warm waters. Ingesting uncooked or undercookedshellfish that contain vibrios, especially oysters, transmits it. Aftera brief incubation period, often as short as two hours, VibrioVulnificus causes septicemia and cellulitis. Physical symptoms includeindigestion, cramps, nausea, vomiting, headache, weakness, fever andchills.

[0007] Usually, this food poisoning subsides spontaneously within twodays. Occasionally, however, it is more severe. Persons withpre-existing hepatic disease or compromised immune system are especiallyin danger. Infection may occur not only through digestion of raw seafoodbut also from wound infection following exposure to seawater.

[0008] While fatal outcomes are extremely rare, the unfortunate eventshave been widely publicized, making the public aware of a potential lifethreatening exposure to the Vibriones. The fear of the bacteriapoisoning is so high that the federal government issued a specialwarning advising the public of the potential dangers of raw oysterconsumption. It has also been suggested that no harvesting of oysters beconducted during warm months in the Gulf of Mexico, so as to minimizethe health risk associated with such food poisoning.

[0009] Public fear of the potential dangers associated with bacteriapoisoning through raw oyster consumption adversely affected an importantLouisiana industry—oyster harvesting. Market share of Gulf oystersshrunk, and many fishermen found that even oysters harvested from safebeds are not in such a great demand as they used to be and that theprice has fallen drastically.

[0010] Still, consumption of raw molluscan shellfish is so widespread inthe South that many restaurants continue to carry raw oysters as part oftheir menu. Even though many restaurants post a warning sign of thepossible danger to a segment of the public with liver or immune systemdisorders it rarely stops dedicated gourmands.

[0011] To prevent poisonous consumption of pathogenic organisms, variousmethods have been suggested for treating raw shellfish, for example withheat or irradiation, in an effort to eliminate or minimize the publichealth danger. For example, U.S. Pat. No. 5,679,392 (the '392 patent)issued on Oct. 21, 1997 for “Heat Treatment of Raw Molluscan Shellfish”discloses a method for preparing raw molluscan shellfish in the shell orout of the shell employing a mild heat treatment and cold storage.

[0012] According to the '392 patent, the shellfish placed in a polymeror metallized bag is lowered into a circulating bath of water at atemperature of between 120° F.-130° F. for 30-45 minutes, after whichtime it is cooled in a cold water bath to a temperature between 28°F.-32° F. The product is then transferred to a cool water bath, where itis retained for 15-20 minutes and becomes ready for storage in arefrigerated state at 32° F.-34° F. The patent disclosure asserts thatthe mollusk remains in a raw state and in the shell throughout theprocess, while the number of pathogenic bacteria is reduced to anundetectable level.

[0013] While this process may be satisfactory for some products, it isbelieved that heating of the shellfish will affect the sensory qualitiesof the product, making it less desirable for consumption as rawshellfish. Heat treatment as a means of controlling microorganisms andbacteria in food products results in diminished taste and reducednutritional content. Therefore, elevated temperatures are consideredunsatisfactory for processing of raw oysters where the purpose of theprocess is to retain sensory qualities of oysters and sell them on ahalf-shell.

[0014] Ionizing irradiation was tested as one of the methods ofdestroying harmful bacteria in live shellfish. However, this process isrelatively expensive and has not yet obtained approval by the FederalFood and Drug Administration. Other known attempts to purify raw oystersinvolve depuration, wherein oysters are soaked in a tank of water fordays at a time in an attempt to purge and cleanse the mollusk of thebacteria. So far, there have been no reports on the success of thismethod in destruction of bacteria in raw oysters.

[0015] Other suggested methods of destroying Vibrio Vulnificus involvecold, freezing, vacuum packaging, use of GRAS (diacetyl) compounds,suspension relaying into offshore water, and food condiment treatment.While some of these methods are relatively simple to implement, most ofthem have problems—either too expensive, ineffective, time consuming, orfailed to receive FDA approval.

[0016] It was also suggested to refrigerate oysters immediately afterharvesting at 7.2° C. or less in an attempt to control multiplication ofbacteria. However, cold treatment greatly reduces but does not eliminatebacteria present in oysters during harvesting for a storage periodconsidered normal for shucked or shell stock oysters.

[0017] Heat treatment, for example at 50° C. for 10 minutes, kills thebacteria; this method is currently used on a commercial scale for liveshell stock oysters. However, this method also kills the oysters.Additional drawback of this method is that it is difficult to controlthe temperature of commercial size batches when the size and shellthickness of oysters differ from batch to batch.

[0018] Vacuum packaging combined with freezing tends to reduce the levelof Vibrio Vulnificus. However, this method is relatively expensive,reduces quality, so that the product treated in this manner may not finda wide acceptance with the public. When diacetyl, an FDA approvedpreservative was used on raw oysters, at levels of 0.05% or greater, itdemonstrated decrease in the level of the bacteria, but did notguarantee complete elimination thereof.

[0019] When oysters were relayed into high salinity environment ofoffshore waters, Vibrio Vulnificus bacteria were reported to decrease toa level found in oysters normally harvested in more cold months, whereno reported cases of food poisoning were recorded. However, oysterpredators and parasites are a factor with this very expensive method.The use of UV light and micro-filtration treatment of seawater did notdepurate the bacteria from oyster tissue.

[0020] Some studies examined the effect of Tabasco sauce on freshlyshucked oysters. In about ten minutes, the level of Vibrio Vulnificus onthe surface of tested oysters was significantly reduced, but the levelsof the bacteria within the oyster meat remained almost unaffected.

[0021] In recent years, a new technology has emerged—high pressureprocessing of foods. The leading manufacturer of high-pressure foodprocessors is ABB Pressure Systems AB of Vasteras, Sweden and itsaffiliate, ABB Autoclave Systems, Inc. of Columbus, Ohio. According toindustry sources, this company makes equipment for processing of juices,fruits, vegetables, fruit-based beverages, jams, sauces, soups andmeats. The company's literature claims that most bacteria in food can bekilled by pressures in the range of 400-800 MPa (58,000 p.s.i. -116,000p.s.i.).

[0022] A Canadian company, GEC ALSTHOM, developed a cold pasteurizingsystem, which utilizes high hydrostatic pressure for processingthermal-sensitive packaged food products. According to that company'sliterature, pressure modifies cell membrane permeability ofmicroorganisms. As a result, bacteria are inactivated or die. It isrecommended that the treated products are kept chilled at 4° C. in orderto reduce bacteriologic risk. The process is said to triple shelf lifeof the products.

[0023] Other companies in Europe and the United States continue researchin the high-pressure food processing area.

[0024] High pressure is said to be preferable to heat treatment becausehigh pressure does not destroy many of the substances found in freshfoods, such as vitamins, chlorophyll and aroma substances. As a result,refrigerated shelf life of fruit and vegetable products, as well ashigh-acid products can be increased from several weeks to severalmonths. Most importantly for the purposes of the present invention, highpressure treatment is believed to increase food safety by reducingbacteria in the processed products, while retaining the products'nutritional value, color, flavor and texture.

[0025] The principle of cold isostatic (uniformly applied) pressureprocessing is relatively simple—food is placed in a container and issurrounded by a pressure medium, usually water. An external pressureintensifier to a predetermined value pressurizes the vessel. Pressure isfed into the pressure vessel where food products have been deposited.Pressure in such a vessel is distributed evenly through all parts of theproduct, thereby preventing mechanical damage of delicate food products.The process may be conducted with no or minimal heat treatment.

[0026] Another problem that the present invention addresses ismechanical shucking of oysters. Seafood processing plants employskillful workers for the preparation of oysters for packaging in jarsand other containers for sale to the customers. Restaurants that serveraw oysters also employ special personnel for shucking oysters beforeserving the delicacy on a half shell.

[0027] The process of oyster shucking involves cutting of the connectivetissue of oyster adductor muscle that is normally attached to the shelland keeps the shell halves tightly closed. More experienced workersperform this task relatively well, while novices can damage the productand cut through the body of the oyster, thereby reducing the quality andincreasing the cost.

[0028] At present, the applicant is not aware of any commercial utilizedmethod of mechanical shucking of oysters. It is estimated that about 80%of the cost of a shucked oyster are due to the labor-intensivehand-shucking process.

[0029] The present invention contemplates elimination of drawbacksassociated with the prior art and reduction or elimination of harmfulbacteria in raw shellfish, as well as shucking of oysters without anysubstantial affect on the sensory qualities of raw shellfish.Additionally, a new method of fabricating the yoke and chamber of highpressure equipment is disclosed.

SUMMARY OF THE INVENTION

[0030] It is, therefore, an object of the present invention to provide aprocess for reducing or elimination of pathogenic organisms from rawmolluscan shellfish, such as oysters, clams, and mussels.

[0031] It is another object of the present invention to provide a methodof reducing harmful bacteria in raw shellfish without substantiallyaffecting its sensory qualities.

[0032] A further object of the present invention is to provide a methodof shucking oysters and other shellfish such as clams and mussels thatdoes not involve manual cutting of the oyster muscle.

[0033] Still another object of the present invention is to provide anapparatus for high pressure processing of shellfish, such as oysters,clams and mussels.

[0034] These and other objects of the present invention are achievedthrough a provision of a process that includes high-pressure treatmentof raw shellfish, the process comprising the step of exposing theshellfish to relatively high hydrostatic pressure. The process isconducted at ambient temperatures, exposing the molluscan shellfish tothe liquid pressure of between 20,000 p.s.i. to 80,000 p.s.i. for 1-15minutes.

[0035] As a result of the high-pressure treatment, pathogenic organisms,such as bacteria Vibrio Vulnificus are destroyed without substantiallyadversely affecting the sensory qualities of the shellfish. At the sametime, the connective tissues of oyster adductor muscle holding the twooyster shell halves is separated from the shells, and the oyster shellsopen without any manual cutting of the muscle.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Reference will now be made to the drawings, wherein like partsare designated by like numerals, and wherein FIG. 1 is a schematic sideview of high pressure processor for practicing the process of thepresent invention.

[0037]FIG. 2 is a top view of the processor shown in FIG. 1; and

[0038]FIG. 3 is detail cross sectional view of the inner liner with topand bottom lids and pressure containing seals.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0039] The new process for the treatment of raw molluscan shellfishaccording to the present invention will now be described in more detail.According to this process, raw shellfish, such as oysters, clams andmussels are treated in a high-pressure environment with no applicationof heat, at substantially ambient temperatures.

[0040] The non-thermal method of food preservation, high pressureprocessing, has been known in use in relation to meat product, fruits,and other products. However, no attempts have been known so far to treatsuch fragile, easily damaged products as raw shellfish. Traditionally,shellfish, such as crab, crawfish and oyster deteriorate in qualityimmediately upon death. For this reason, they are usually shipped eitherlive, at considerable expense in refrigerated containers, or freshfrozen.

[0041] None of these approaches could be applied to insure bacteria-freeraw shellfish that would satisfy public demand for raw oysters eaten ona half shell. Bearing in mind the importance of regaining markets andconsumer confidence in Gulf oysters, fishermen are looking for feasiblemethods of processing shellfish without destroying its nutritional andsensory values.

[0042] According to the present invention, molluscan shellfish, forexample, shellstock oysters, are individually tied with a flexible band,for example a rubber band, and placed in a pressure vessel that containsa pressure transmitting fluid, for example, water. If desired, theshellfish can be prepackaged in pouches and then loaded into thepressure vessel. The vessel is then closed and pressurized to betweenabout 20,000 p.s.i to 50,000 p.s.i. for 1-15 minutes.

[0043] During experimental tests, it was observed that the higher thepressure, the less time it takes to destroy bacteria, such as VibrioVulnificus in raw oysters. For example, when shellstock oysters weretreated at hydrostatic pressure of 50,000 p.s.i. for 5 minutes, seededbacteria Vibrio Vulnificus was reduced from 24,000 MPN/g to 0 MPN/g(here, MPN stands for Most Probable Number).

[0044] During processing, the pressurized liquid remained at ambienttemperature while the pressure was transmitted uniformly to the productinside the pressure vessel. The resultant product did not significantlychange in volume and no mechanical damage was observed to the delicatefood product.

[0045] During experimental tests, it was determined that treatment ofthe product at hydrostatic pressure of 50,000 p.s.i. for 5 minutesachieved the desired result with all of the treated shellfish. It isenvisioned, however, that under certain conditions, the shellfish can betreated at even higher or lower pressures. The increase in temperatureduring the treatment was minimal, about 3° C. per 14,500 p.s.i.; it didnot depend on the size of the processed product. The temperaturedecreased as soon as the pressure application was terminated.

[0046] Some experiments showed that preferred pressures are in the rangeof 45,000 p.s.i., as pressures lower than 45,000 p.s.i. could lead toreversible denaturing of the treated product, and thereby adversely notachieve the desired results.

[0047] It is further envisioned that other types of bacteria, inaddition to Vibrio Vulnificus can be eliminated or substantially reducedin raw shellfish with the use of the present invention, thereforeincreasing the shelf life of a product.

[0048] During experiments with raw oysters, an unexpected phenomenon wasobserved the oyster adductor muscle connective tissue attachment at theshell denatured to gel formation at pressure as low as 20,000 p.s.i. andtreatment time of 15 minutes. First, it was observed that a gapdeveloped between the shell halves. When the shell halves were priedopen, the oyster easily slid out of the shell in perfect condition. Nomechanical cutting was necessary. The denaturing of muscle proteins,including actin and myosin and connective tissues to a gelatintransition is a result of disruption of non-covalent interactions intertiary protein structures. The potential commercial utilization ofthis chemical denaturing for mechanical shucking of live shell stockoysters has not been previously tested or observed.

[0049] To prevent escape of water or “bleeding” of oysters during thehigh pressure treatment, oysters need to be mechanically banded, forexample with a flexible band, such as a rubber band, before placement inthe processing vessel. The band keeps the shell halves tightly closed,thereby helping in preservation of natural condition of raw oysters thatcan be later served on a half shell. The processed oysters can beshipped to customers with the bands attached, and the consumer will thenonly need to remove the band to open the oysters. Oysters that will beimmediately shucked do not need to be banded.

[0050] Turning now to the drawings in more detail, numeral 10 designatesa high-pressure processor used in the present invention. The processor10 comprises an enclosure 12 made of steel or stainless steel. Theenclosure 12 has a bottom plate 14 and four vertical sidewalls (only twoopposing sidewalls 16 and 18 are shown in FIG. 1).

[0051] The enclosure 12 can be mounted in a cavity 20 formed below afloor level 22. Concrete walls reinforced with rebars, if necessary candefine the cavity 20. The walls and floor defining the cavity 20 may be12″ or more in thickness. At the least a lower portion of the enclosure12 is housed within the cavity 20.

[0052] A first pressure vessel 30 is secured on the wall 16 of theenclosure 12 by attachment brackets 32. The brackets 32 are verticallyspaced from each other and can be three or more in number. The vessel 30has vertical walls 34 a, 34 b, 34 c, and 34 d (see FIG. 2), a bottom lid36 and a top lid 38 with four vertical corner bars 39 (FIG. 2).

[0053] A continuous cylindrical liner 40 is mounted inside the vessel30, the liner 40 extending from a level adjacent the bottom lid 36 tothe upper edge of the vessel 30. The liner 40 defines a pressure chamber42 inside the vessel 30. Horizontal slabs 44 surround the vertical liner40, and a safety plate 46 is secured on the exterior of the vessel 30,extending along the wall 34 b, as can be better seen in FIG. 2. Theslabs 44 can be made of high tensile steel or other high-tensilematerial to help contain the high pressure created in the chamber 42.The top lid 38 and the bottom lid 36 have central portions, 37 and 35,respectively, that extend into the cylindrical liner 40, as can bebetter seen in FIG. 3. Pressure containing seals 39 are positioned in acircumferential relationship about the portions 35 and 37 between theliner 40 and the central portions 35, 37.

[0054] A second pressure vessel 50 is securely attached on the oppositewall 18. The second pressure vessel 50 is similar to the first pressurevessel 30 in all respects, as it comprises a cylindrical inner liner 52surrounded by a high-tensile “envelope” 54 placed in the vessel 50. Theenvelope 54, similar to the slabs 44 can be made of a plurality ofsmaller high tensile steel slabs. A plurality of attachment brackets 56secures the vessel 50 on the wall 18. A top lid 58 covers the open topof the vessel 50 and a bottom lid 59 covers the bottom of the vessel 50.The top lid 58 and the bottom lid 59 have central portions, similar toportions 35, 37 of the vessel 30, that extend into the liner 52 wherethe pressure containing seals 39 are located.

[0055] Each bottom lid 36 and 59 is provided with inlet/outlet openingto allow pressure medium fluid to move in and out of the pressurechamber 42 and 51. As can be seen in FIG. 3, the central portion 35 ofthe lid 36 has a central fluid channel 80 that extends to about midwayof the lid 36.

[0056] A second channel 82 fluidly communicates with the first channel80 to allow egress and ingress of pressure fluid. The second channel 82is formed at about a right angle to the first channel 80 extending fromthe center of the lid 36 in a parallel relationship to the general planeof the lid 36 and in a transverse relationship to a vertical axis of theliner 40. The channels 80 and 82 connect the interior of the pressurechamber 42 with an exterior thereof The lid 59 of the pressure vessel 50is provided with an identical inlet/outlet port connecting the pressurechamber 51 with an exterior thereof.

[0057] Extending between the opposing walls 16 and 18 is a pair of rails60, 62. A pressure holding and safety yoke 64 slides on the railsbetween the first pressure vessel 30 and the second pressure vessel 50.The yoke 64 is mounted on wheels 66, which are secured at bottom cornersof the yoke frame. A bottom plate 68 is secured above a bottom part 67of the yoke 64, and a top plate 70 is secured below a top part 71 of theyoke 64. The space between the upper plate 70 and the bottom plate 68 islarge enough to accommodate the pressure vessel 30 or 50. The purpose ofthe bottom plate 68 and the top plate 70 is to provide extra strength tothe yoke 64.

[0058] The yoke 64 further comprises two vertical walls 74 and 76secured in parallel relationship between the upper part 71 and thebottom part 67 of the yoke 64. As a result, a rectangular framestructure is defined by the yoke walls, bottom and upper parts. In use,the yoke 64 surrounds the pressure vessel 30 or 50 on opposite,unprotected walls 34 a and 34 c and provides extra protection when highpressure is applied. The primary function of the yoke 64 is to hold thelids 58 and 59 of the vessel 50 and the lids 36, 38 of the vessel 30 inplace when high pressure is applied.

[0059] The top plate 70 covers the lids 38, 58, while the bottom plate68 extends below the bottom lids 36 and 59 of the vessels 30 and 50,respectively. The yoke walls 74 and 76 and the upper part 71 and thebottom part 67 can be formed from a plurality of high tensile slabssecured together by four bolts. A top safety shield 72 provides extraprotection during operation.

[0060] In operation, raw shellfish, such as an oyster is individuallybanded to prevent escape of water from the shell when the oyster isremoved from the chamber. The oysters are placed in a basket for handingpurposes. Oysters can also be placed in flexible bag filled with waterprior to being inserted into the pressure chambers of vessels 30 and 50.The pressure chamber is filled with pressure medium, such as water. Thebasket is then inserted into the pressure chamber of a vessel 30 or 50,and the lids 38, or 58, respectively, are closed. The yoke 64 is rolledtoward the loaded vessel and secured in place by a conventional stop toassure positioning during a high-pressure application.

[0061] An external pressure source is used for supplying pressure to thepressure chamber of the vessel, where the oysters have been deposited.According to Pascal's Law, this hydrostatic pressure has a uniformeffect on all materials inside the pressure vessel. Equally distributedpressure affects the oyster meat inside the shells and eliminates VibrioVulnificus bacteria from the oyster meat without any mechanical damageto raw oysters.

[0062] Oyster meat has a high water content, which makes high-pressuretreatment a particularly advantageous type of processing for rawoysters. At the same time, the adductor muscle detaches from the shell,and shell halves are ready to separate, when necessary, for servingoysters on half shelf, or for easy shucking of oysters.

[0063] While the oysters are processed, the pressure in the chambers 42or 51 is rapidly elevated to between 20,000 p.s.i. and 50,000 p.s.i. Thepressure is retained for about one to fifteen minutes, depending on theselected pressure value. For lower pressures, the time of treatment isgreater, while higher pressure requires less treatment time. Thepathogenic microorganisms are eliminated, while nutritional value andsensory qualities of raw oysters are not affected.

[0064] Experiments conducted with raw oysters demonstrated that VibrioVulnificus bacteria were eliminated at every test run with any sizeoysters when pressure was in the range of 45,000 p.s.i. and treatmenttime was about 5 minutes. Shucking of oysters occurs at much lowerpressures, about 20,000 p.s.i., when oysters are treated for 15 minutes.Therefore, it is envisioned that for processes not requiring bacteriaelimination, but only shucking, the vessels 30 and 50 can be run atlower pressures.

[0065] Once the batch in the loaded vessel has been treated for thepre-determined period of time, the yoke 64 is rolled away from thatvessel and engaged with the second vessel. While the product isprocessed in the second vessel 50, the treated product from the firstvessel 30 can be unloaded, and a new batch of products depositedtherein. The single yoke 64 serves as a pressure holding and safetydevice for two separate pressure vessels 30 and 50.

[0066] The method in accordance with the present invention does notcause thermal damage, as the process is conducted at ambienttemperatures. At the same time, no mechanical damage to the delicateoyster meat occurs, as the shell protects the oyster from any contactwith the mechanical parts of the pressure vessels.

[0067] The method of the present invention has minimal impact on theenvironment. Cooling water can be recycled through the use ofconventional equipment. Conventional electromechanical systems can beused to generate high pressure inside the pressure vessels 30 and 50.

[0068] It is envisioned that various types of molluscan shellfish, suchas clams, muscles, abalone, and others can be processed with the methodof the present invention without mechanical damage or deterioration ofsensory properties of the product. Once the bacteria are eliminated, theproduct can be shipped for consumption in a raw state. It is believedthat the process of the present invention can be implemented forelimination of other bacteria, in addition to Vibrio Vulnificus.

[0069] The shellfish can be harvested even in warm months, and thepublic will be assured of the product safety. Naturally contaminatedGulf Coast oysters that can contain thousands of harmful VibrioVulnificus bacteria can be successfully processed with the apparatus andmethod of the present invention.

[0070] Other seafood items can be similarly processed with the methodand apparatus of the present invention. If desired, oysters and otherproducts to be treated in the system of the present invention can beplaced in baskets in a refrigerator/cooler, so as to prevent bacteriamultiplication, while the products wait their turn in the pressurevessels. After processing, the shellfish should be placed in a cooler assoon as possible. The processed shellfish should be preferably kept atbetween 32° F. and 36° F. until it is sold and consumed by a customer.

[0071] The external source of pressure can be any conventionalpressurizing means, such as hydraulic motor, electrical motor and thelike. Other means for building up pressure in the pressure chambers canbe successfully employed without affecting the advantages affordedthrough the practice of the present invention.

[0072] Many changes and modifications can be made in the process of thisinvention without departing from the spirit thereof. I, therefore, praythat my rights to this invention be limited only by the scope of theappended claims.

In the claims:
 1. A method of eliminating pathogenic organisms in rawshellfish, comprising: exposing raw shellfish to hydrostatic pressure atambient temperature for a period of time sufficient to cause destructionof the pathogenic organisms without substantially affecting sensorycharacteristics of said raw shellfish.
 2. The method of claim 1, whereinsaid raw shellfish is exposed to hydrostatic pressure of between about20,000 p.s.i. to about 50,000 p.s.i. for 1-15 minutes.
 3. A process ofdestroying bacteria in raw molluscan shellfish, comprising the steps of:providing a pressure vessel; depositing said shellfish into saidpressure vessel; loading a pressure transmitting liquid into saidpressure vessel; pressurizing said pressure vessel to between about20,000 p.s.i. and 50,000 p.s.i., thereby causing destruction of saidbacteria, while retaining sensory characteristics of said shellfish. 4.The process of claim 3, wherein said raw shellfish is exposed toisostatic pressure for 1-15 minutes.
 5. A raw shellfish treated inaccordance with the process of claim
 3. 6. A process of treating rawmolluscan shellfish, which comprises: exposing said shellfish to ahydrostatic pressure of between 20,000 p.s.i. to 50,000 p.s.i. for 1-15minutes at ambient temperature, thereby destroying pathogenic organismsin said raw shellfish.
 7. The process of claim 6, wherein said shellfishis enclosed in liquid-impermeable bags filled with pressurizable liquidprior to exposing said shellfish to hydrostatic pressure.
 8. A method ofshucking a raw oyster, comprising the steps of: exposing said oyster tohydrostatic pressure sufficient to cause detachment of an adductormuscle from a shell of said oyster and opening of the oyster shell. 9.The method of claim 8, wherein said oyster is exposed to hydrostaticpressure of at least 20,000 p.s.i. for 15 minutes.
 10. The process ofclaim 8, wherein a flexible detachable band is wrapped around saidoyster shell prior to exposing said oyster to hydrostatic pressure. 11.A process of shucking oysters, comprising the steps of: wrapping aflexible detachable band around individual oysters; positioning saidoysters in a pressure vessel; applying hydrostatic pressure to saidoysters in the pressure vessel for a time sufficient to cause detachmentof an adductor muscle from shells of said oysters; removing said bandsfrom said oysters and opening said oysters without cutting said adductormuscles.
 12. The process of claim 11, wherein said oysters are exposedto hydrostatic pressure of at least 20,000 p.s.i. for a period of about15 minutes.
 13. The process of claim 11, wherein said oysters arepositioned in flexible liquid-impermeable bags filled with pressurizableliquid prior to exposing said oysters to hydrostatic pressure.
 14. Anapparatus for processing raw food products, comprising: a pressurevessel having a bottom plate, vertically extending side walls and adetachable lid; a liner positioned inside said pressure vessel, saidliner defining a pressure chamber for receiving said raw food products,said pressure chamber being adapted for pressurization by an externalsource of pressure; retaining members positioned in said pressure vesselaround said liner, said retaining members being formed from ahigh-tensile steel; a pressure-holding and safety yoke being adapted forpositioning around said pressure vessel when said pressure chamber ispressurized.
 15. The apparatus of claim 14, wherein said retainingmember is comprised of a plurality of high-tensile steel slabs sized andshaped to conform to exterior walls of said liner.
 16. The apparatus ofclaim 14, further comprising a means for mounting said vessel on avertical surface in an elevated position relative to a horizontalsurface.
 17. The apparatus of claim 16, further comprising a safetyplate secured on a side wall of said pressure vessel opposite saidmounting means.
 18. The apparatus of claim 16, wherein said mountingmeans comprises a plurality of brackets fixedly attached to the exteriorwall of said pressure vessel.
 19. The apparatus of claim 14, whereinsaid yoke is mounted on wheels to facilitate movement of said yoke inrelation to said pressure vessel.
 20. The apparatus of claim 19, furthercomprising a means for aligning said yoke when said yoke moves inrelation to said pressure vessel.
 21. The apparatus of claim 20, whereinsaid aligning means comprises a pair of rail guides, and wherein saidwheels engage in said rail guides.
 22. The apparatus of claim 14,wherein said yoke is sized and shaped to cover said bottom, said top andat least a part of said side wall of said pressure vessel.
 23. Anapparatus for processing raw shellfish to eliminate bacteria in said rawshellfish, said apparatus comprising: a first pressure vessel, a secondpressure vessel, said pressure vessels being adapted to receive said rawshellfish therein, each of said pressure vessels comprising a pressurechamber for receiving a pressure transmitting liquid therein and forcreating a pressure of between 20,000 p.s.i. and 80,000 p.s.i.; apressure holding and safety yoke movable between said first pressurevessel and said second pressure vessel for selectively holding pressureand protecting said first pressure vessel and said second pressurevessel, when said raw shellfish is loaded in any of said pressure forpressure processing, said yoke holding lids of said pressure vesselsduring a pressure-application cycle.
 24. The apparatus of claim 23,wherein each of said pressure vessels comprises a liner for defining apressure chamber and retaining members mounted in said pressure vesselaround said liner.
 25. The apparatus of claim 24, wherein said retainingmembers are formed from high tensile steel slabs.
 26. The apparatus ofclaim 24, wherein said retaining members comprise a plurality of hightensile steel slabs secured together to conform to the size and shape ofan interior wall of said pressure vessel and an exterior wall of saidliner.